SBIR Phase I: Affordable Onsite Wastewater Treatment Solution

The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project is to provide homeowners with an affordable on-site wastewater treatment solution. Hawaii’s coral reefs are under threat from products of hundreds of thousands of onsite treatment systems across the state seeping into the groundwater and eventually reaching the coastal ecosystem. The proposed onsite wastewater treatment technology could will address this with wide-ranging environmental benefits. The State of Hawaii has legislated the replacement of residential cesspools by 2050 in order to reduce the pollution in streams and the ocean. Unfortunately, upgrade costs are so high that 90% of Hawaiian cesspool owners can’t afford the upgrade. The proposed technology can reduce the cost of upgrades by 5-10x. While the initial application will be in Hawaii, the technology will have national applicability. The proposed system uses an algal bacterial biofilm to passively aerate wastewater recirculated from a septic tank to conduct nitrifying, denitrifying, and heterotrophic operations. Previous investigations into abPBR use for onsite treatment have shown the capacity for high nutrient and BOD removal, but only with active maintenance and pumped recirculation. This project proposes a novel system with this performance but without high maintenance or energy demands. A novel convection-based passive recirculation process will be the primary focus of this study, with a focus on determining how experimentally determined passive recirculation rates and internal temperatures align with computational models, as well as standards for on-site residential wastewater treatment systems. The project will also explore susceptibility to and impact of disrupted recirculation due to gases coming out of solution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.